ISTANBUL — In a signal that Turkey faces indefinite rule by decree, President Recep Tayyip Erdogan announced on Sunday that a state of emergency, introduced as a temporary measure after last year’s failed coup, would continue until the country achieved “welfare and peace.”

The state of emergency allows Mr. Erdogan and his cabinet to issue sweeping decrees without parliamentary oversight or review by the constitutional court, giving him an almost untrammeled grip on power.

So far, the decrees have allowed Mr. Erdogan to jail more than 40,000 people accused of plotting a failed coup, fire or suspend more than 140,000 additional people, shut down about 1,500 civil groups, arrest at least 120 journalists and close more than 150 news media outlets.

Despite international criticism of these measures, Mr. Erdogan said on Sunday that the state of emergency “will not be lifted,” according to Anadolu Agency, a state-owned news wire. “Until when? Until the situation reaches welfare and peace.”

A recent referendum victory gave Mr. Erdogan the power to rule by decree from 2019 onward, provided that he wins presidential elections held that year. But his announcement on Sunday means he can continue to wield such power in the intervening period.

International rights groups say that while the state of emergency was initially justified because it followed a coup attempt that left at least 249 people dead, it is now being used as a pretext for quashing dissent.

“What we’ve seen is that instead of using the state of emergency to counter genuine threats to national security, it’s been abused to stifle criticism of the ruling A.K. party,” said Andrew Gardner, a Turkey researcher for Amnesty International, using the Turkish initials for Mr. Erdogan’s Justice and Development Party. “And there’s every signal that that will continue.”

Amnesty says it will publish a report on Monday detailing the “catastrophic impact” that the state of emergency — and the purges it has precipitated — has had on the lives of hundreds of thousands of Turkish families. “More than 100,000 people have not just lost their jobs, in a completely arbitrary process, but had their professional and personal lives shattered as well,” Mr. Gardner said.

As far back as December, legal experts from the Council of Europe, an influential pressure group, warned that if the Turkish government “rules through emergency powers for too long, it will inevitably lose democratic legitimacy.”

In his speech on Sunday, Mr. Erdogan shrugged off these concerns. “In my country, they tried to overthrow the state, and we gave 249 martyrs, and had 2,193 injured,” he said in remarks carried by Anadolu Agency. “How dare you ask us to lift the state of emergency.”

Mr. Erdogan spoke at a conference for his party, at which he was formally reaccepted as leader. Mr. Erdogan left the party in 2014 to assume the presidency, an office that was then meant to be politically neutral; last month’s referendum removed that requirement, allowing Mr. Erdogan to rejoin his party.

His comments capped a turbulent week for him. In a visit to Washington on Tuesday, Mr. Erdogan failed to persuade President Trump to abandon an alliance with a group of Syrian Kurdish fighters whom Turkey regards as terrorists. Later in the day, Mr. Erdogan watched silently as his bodyguards assaulted several people protesting his policies.

Correction:May 21, 2017

An earlier version of this article misstated the circumstances under which Recep Tayyip Erdogan departed the Justice and Development Party. He left to assume the presidency, not to run for it.

A version of this article appears in print on , on Page A6 of the New York edition with the headline: Erdogan Extends His Far-Reaching Rule Over Turkey. Order Reprints | Today’s Paper | Subscribe